Automatic assembly machines for electronic components conventionally have a pickup head, which fetches electronic components from different magazines and mounts them on accurately determined locations on a circuit board. The transport from a magazine requires a certain amount of time. Different suggestions have been made earlier and have also been implemented in present machines in order to reduce this amount of time, which can be troublesome and result in the assembly operation requiring a long time in the case where many components are to be mounted on each circuit board and the pickup head can only transport one component in a movement from a magazine to the board.
In IBM Technical Disclosure Bulletin, vol. 28, No. 11, April 1986, pp. 4764-4765, "Chip Transfer Head with Programmable Probe Centerlines", a chip transfer head is disclosed for transferring multiple chips from one type of device carrier to another type of device carrier. Four vacuum probes are used and their lateral position in relation to each other can be adjusted. Also, one or more of the probes can be retracted by means of miniature air cylinders if all probes are not needed.
In IBM Technical Disclosure Bulletin, vol. 17, No. 7, December 1974, pp. 1876-1877, L. G. Call et al., "Electronic Component Assembly Apparatus", a single multisection ram is disclosed having four independent sections. A selector block's slide is engageable in adjacent ram sections. The selected ram sections can be moved vertically by means of an operating cylinder. The ram sections can only be selected in some limited patterns and are thus not controlled individually.
In IBM Technical Disclosure Bulletin, vol. 22, No. 7, December 1979, pp. 2757-2761, K. G. Hoebener, "Multiple Size Chip Pickup, Orientation and Placement Station", a chip placement station is disclosed having a transfer arm. To fixed locations on the transfer arm probes are attached, two for transfer of chips from delivery stations to orienting stations and one from an orienting station to station holding a substrate. The transfer arm moves the probes as one unit in one horizontal direction and in a vertical direction.
In Swedish Patent Applications SE-A 8203546-0, corresponding to U.S. patent application having Ser. No. 06/271,835, now U.S. Pat. No. 4,450,619, and SE-A 8203511-4, corresponding to U.S. patent application having Ser. No. 06/271,836, now U.S. Pat. No. 4,387,506, both filed Jun. 9, 1981 for H. L. Wright et al. and assigned to USM Corporation, an apparatus is disclosed for mounting components individually selected from magazines. Two pickup devices are movable independently along a front side and a rear side of vertically arranged magazines.
The U.S. Pat. No. 4,951,383 and the European patent application EP-A2 0 373 373, for which convention priority is claimed from the same three Japanese patent applications, disclose an automatic mounting apparatus comprising a pickup head 10 having three or more vertically movable pickup devices 41. each one having a vacuum nozzle 45 (11). The pickup devices comprise vacuum channels for holding the nozzle and the component to be mounted, and are driven vertically (z-direction) by a drive mechanism 43, consisting of a drive motor 67, a ball screw 68, a vertically movable nut 69 and a movable plate 70 connected to the nut and having a number of engagement pins 71. When the motor 67 is activated, the plate 70 is driven vertically (along guides 72), which in turn drives the pickup devices vertically by means of the pins 71 supporting the lower sides of flanges 54 mounted to the pickup devices. The pickup devices are further locked in an upper position by blocking levers 63 which are controlled by solenoids 65 and in a deenergized state thereof are locked, these means then engaging the lower sides of the flanges 54 of the pickup devices. In the energized state, the pickup devices are free to move and will then rest on the support pins 71. The pickup head can then, by being driven by a single motor, individually and selectively control the pickup devices for picking a number of components simultaneously. Furthermore, the pickup devices can be also individually controlled to be turned to a desired angular position by means of individual drive motors 77, that are each coupled to its own pickup device.
The Japanese patent application JP-A 6-37486 discloses an automatic assembly machine comprising a number of pickup devices. In e.g FIG. 14, a pickup head is illustrated comprising at least two pickup devices 14 having vacuum nozzles, which seem to be spring-loaded (41) to a projected, lower position, and locked in an upper position by the operation of locking arms 44, which, however, are not individually operative. A similar machine is disclosed in the Japanese patent application JP-A 4-241499.
The Japanese patent application JP-A 64-2400 discloses a mounting machine comprising a pickup head having a number of spring-loaded (33) pickup devices locked in an upper position by blocking arms 36. One arm at a time can be operated for un-locking a selected pickup head.
The European patent application EP-A1 0 434 156 discloses a pickup head for e.g. an assembly machine comprising a number of pickup devices 3 which are mounted in parallel and can be driven to desired angular positions by means of crank arms 13, a coupling rod 15 and a single drive motor 36. Each pickup device can be driven individually to pick or place a component.
The Japanese patent applications JP-A 6-177 592 and JP-A 6-61692 and the European patent application EP-A1 0 578 136 also disclose assembly machines having pickup devices which in some cases appear to be individually operative.